eth0 won't stay up

[hanfamily at earthlink.net]

I just reinstalled fedora core 3 to solve the dual boot problem. This time
I did graphical install so I had a minimal choice so I would have fewer
packages to remove instead of a text install. I do not know what I did
different but I created a huge problem with eth0 my log is full of the
following
May  4 10:38:05 jupiter kernel: eth0: link up, 100Mbps, half-duplex, lpa 
0x40A1
May  4 10:38:06 jupiter kernel: eth0: link down
repeated ever fraction of a second. Any ideas what I need to do? I made
a copy of ifconfig output, route and alot of files in /etc in case they
would be helpful.
                     Thanks
                     Linda